The newborn baby fitted so perfectly into her arms, it felt as if that was what they had been designed for. The pink, downy cheeks, the shock of damp, dark hair, the shell-like nails on the wrinkly little fingers, 26-year-old Eleanor feasted on every detail.

But these moments of bliss were always brief. In a few moments, she’d hand the baby back to his mother and jump into her little car and drive across Liverpool’s poorest streets to the next pregnant woman who needed her care.

Poignantly Eleanor knew such moments could never be hers. For as well as being a midwife, she was also a nun. But lately, however, she’d been feeling more than a glow of professional pride when holding a newborn.

Happy: Author Eleanor Stewart, 70, left a life of religious contemplation for a family life and children

Convent: Eleanor (pictured with her brother) became a nun at the age of 18 in 1960

It was rapidly becoming a pang of longing that was making her question whether, rather than the life of celibacy and religious obedience to which she’d been committed since the age of 18, she was, in fact, destined to be a wife and mother after all.

Could these feelings have anything to do with the charming young doctor who was making Eleanor’s heart flutter on her ward rounds? They’d never so much as accidentally touched fingertips, but when Eleanor looked at him, her feelings — toward God, her future, everything — became unbearably confused.

It’s a story which could be straight out of TV’s Call The Midwife. But this dilemma was all too real.The year was 1967; and the city Sister Eleanor criss-crossed in her veil and long habit was the Liverpool of the Beatles, not the East End of post-war London, as in the much-loved BBC series.

Like the on-screen nuns of Nonnatus House, Eleanor’s life centred around prayers and hymns in the chapel; like them, she would drop everything and race out with her medical bag when a woman went into labour.

'I was surrounded by fertility, and I began to feel a terrific longing to have a child of my own,' she remembers. 'My body was crying out to carry a child and to give birth.'

In the hands of a BBC scriptwriter, of course, Eleanor would fall into her dashing doctor’s arms and a wedding and babies would swiftly follow. But this was real life, and her path from convent to motherhood was set to follow a much more rocky road.

The young doctor, Eleanor thinks, was simply the catalyst in her decision to leave the sisterhood. 'He wasn’t especially handsome, but we got along very well,' she recalls today. 'We had the same sense of humour, and there was definitely a spark between us.'

After much agonised soul-searching, Eleanor sought advice from the priest who came to hear the nuns’ confessions. His verdict was clear: Sister Eleanor had lost her vocation. 'I was sad,' she says. 'But I knew he was right.'

A few months later, now going by her birth name of Eleanor Stewart, she stepped out of the convent and back into the world — a world that, in 1968, was very different from the one she had left behind in 1961.

'So much had happened while I’d been inside: pop music, the mini skirt, bee-hive hairdos, free love,' she says. How would she cope?

It was, she admits, a traumatic transition, and she still feels its devastating effects today.Looking back, Eleanor, now a youthful-looking 70, says she was, quite ironically, a very sophisticated teenager when she entered the convent of the Sisters of Charity of Our Lady of Evron.

Swap: Eleanor gave up her life as a nun and midwife because she was desperate for a baby of her own

'My father was in the Army, so I’d lived abroad and had travelled a lot, and I’d also had a boyfriend and had lost my virginity a few months before I entered the convent,' she says.

'It was quite unusual in those days to sleep with a boyfriend while you were still a teenager, but I’m afraid I was a bit of a wild child. I think my mother was quite pleased when I announced I was going to enter a convent.'

Raised a Catholic, Eleanor had become captivated by the romance and sense of adventure life in a convent seemed to offer.

'I got to know some of the Sisters of Charity and their life, as teachers and nurses, seemed perfect. Plus I’d be joining the mother house in France, which seemed a very exciting adventure.'

And so in 1961, aged 18, she said goodbye to her parents in Oxfordshire and travelled to La Mayenne in northern France. Six months later, she was 'clothed' as a ‘bride of Christ’ and became a novice, before taking up teaching English in one of the order’s schools.

Although Eleanor had experienced sex as a teenager, she didn’t miss physical relationships. But she did miss the admiring looks of men.

'I’d been slim and attractive as a young woman, and I was used to being noticed. As a nun I got quite plump and I started wearing glasses — and I did miss not turning heads.'

In 1964, having taken her vows of poverty, chastity and obedience, Eleanor was sent back to the UK to train as a nurse. Her new convent was in Liverpool, and she worked at the city’s Broadgreen Hospital, and fell in love with her new vocation, especially midwifery.

'I absolutely adored delivering babies. The birth rate in Liverpool at the time was going through the roof, so there was never a dull moment.'

Most of her patients were impoverished and living in cramped conditions, and the majority still gave birth at home — she carried stacks of newspapers with her, she says, because clean newsprint was considered a better landing-place for newborns than dirty bedlinen.

Midwife: Eleanor spent her convent days working as a midwife but the experience made her long for children

Joy: Eleanor with her much-loved daughter Esme. A son named Sean followed and she is now a granny

But in the wider world of the Catholic Church, times were changing: religious reforms meant nuns were given new freedoms, and many were abandoning their orders.

'I saw a lot of nuns leaving who were in their early 40s, who desperately hoped there would still be time to meet someone and have a child,' says Eleanor.

When she followed the same path at 26, Eleanor was more optimistic than desperate, although she admits it was difficult.

'Some of the sisters came to Lime Street station to see me off back home to Oxfordshire, and I wept buckets. In the end, Mother Superior marched me into the bar and ordered a brandy, telling the barman it was for health reasons.'

At first, being back in the world was odd. After so many years clad in her long habit, the air on her legs and the wind in her hair seemed strange. So did the fashions.

'I had a neat grey suit, but the skirt came down to my knees and I soon realised it was hopelessly out of date,' she says.

She lost weight, aided by a newly acquired heavy smoking habit, and got contact lenses. 'Before long, I was wearing shorter miniskirts than anyone else and diving into the culture of the Sixties for all I was worth.' And that meant finding boyfriends — and sleeping with them.

'My first lover after I came out of the convent was a young doctor from New Zealand. He was charming, and when he went back home, he asked me to go with him. But it was too soon to make a decision that big. In the end, we had to part.'

There was one amusing occasion when her old life came back to haunt her: working in a hospital in Chichester, she recognised a doctor from her Liverpool days.

'He had no idea who I was. I said, "Don’t you remember me? I was Sister Eleanor!" He was amazed. We went out for a drink and he couldn’t believe this mini-skirted girl had been the nun in her veil and habit.'

Kicking the habit: Eleanor has now written a book that tells her remarkable life story

There was no spark with that particular doctor, but there was with others, and with her New Zealand beau now off the scene, Eleanor threw herself into the 'free love' of the time.

'I didn’t have endless partners, but there were certainly several,' she says. 'And I’m sorry to say that we weren’t always very sensible. We didn’t always use protection.'

The big fear in those days, she says, was unwanted pregnancy. 'No one was thinking about STDs, especially not STDs that could make you infertile,' she remembers.

But when she felt a dull abdominal ache that never seemed to go away, and developed a fever, her doctor diagnosed chlamydia, and discovered the infection had advanced to the point where Eleanor had to have an ovary and fallopian tube removed. Worse, she was warned that if she ever wanted to have children, she’d be at high risk of an ectopic pregnancy.

'It was a crushing blow,' she says. 'Especially given that I’d met the man who I wanted to marry; a wonderful man called John Richardson, now 68, who worked in personnel for a computer company.'

The couple married in November 1973, when Eleanor was aged 30, and started trying for a baby.

'We were hoping against hope that everything would be ok and that I’d be able to carry a child,' she says. 'And when I got pregnant almost straight away, I was absolutely thrilled.

'But at about eight weeks everything came crashing down: I had a terrible pain and had to be rushed to hospital by ambulance. There they confirmed our worst fears; the baby was growing in my remaining fallopian tube, and the only way to save my life was to remove both it and the embryo.'

What that meant, Eleanor knew, was that she could never carry a child of her own. 'I was devastated. It was the one thing I’d hoped for, since back in my convent days. It seemed so cruel that now I’d met John and had everything else I’d dreamed of, I was being denied the baby I longed for.'

IVF, she explains, was still rudimentary, and adoption was their only option. She started the process immediately. Eleanor admits she was partially driven by guilt at not being able to give John a child of his own, and a desperation to 'fix the problem'.

'A few months later I was at work when the phone rang and a voice said, "We think we’ve found a baby for you, Mrs Richardson. Can you come to meet her?"'

The baby was Esme, then nine weeks old. 'People said it would be different because I hadn’t carried her and I hadn’t given birth to her, but actually, it wasn’t,' says Eleanor. 'I loved her from the start, and I loved everything that being a mother involved, as I’d thought I would.'

Three years later, a 17-month-old baby boy, Paul, arrived to complete the family. When Esme was six and Paul was four, the convent in Liverpool invited Eleanor back for an anniversary of their foundation — and she took the children with her.

'I’d always stayed in touch with the nuns through the years, but it was wonderful to be able to introduce them to the sisters. I remember Mother Henrietta saying to me, this is what was meant to be.

'Everything was supposed to happen this way so you could be the mother of these two children.'

Today she and John live in a comfortable house near Portsmouth.Their son, Paul, is now 34 and lives ten minutes’ walk away with his wife and two young sons; four-year-old Joseph and three-year-old Charlie. Esme, who is 36, lives in Suffolk.

'I feel very, very lucky to have all I’ve got,' she says. And just occasionally, on a quiet day, her thoughts go back to the days when she was a nun.

'I’ve never regretted the choice I made,' she says. 'But I’ve never forgotten Sister Eleanor, either.'

Kicking The Habit: From Convent To Casualty In 1960s Liverpool by Eleanor Stewart is published by Lion Hudson, £8.99. Eleanor tweets at @HabitKicking